In general, an aneurysm is a swelling or bulge that forms a cavity in the wall of a blood vessel. One type of aneurysm is a cerebral aneurysm, which forms in an artery of the brain. A cerebral aneurysm may develop suddenly without initial symptoms, and can cause extreme pain. In general, in 15% of cerebral aneurysm cases, the patient dies suddenly upon development of the cerebral aneurysm; in another 15% of cerebral aneurysm cases, the patient dies under medical treatment; and in 30% of cerebral aneurysm cases, the patient survives after treatment but feels an acute aftereffect. As such, a cerebral aneurysm (or any aneurysm) is a very concerning development.
The treatment of aneurysms and other similar vascular disorders often involves the placement of microcoils within the cavity formed by the aneurysm or disorder. Doing so can cause blood to clot, prevent an additional inflow of blood, and decrease the risk of the aneurysm or disorder rupturing (i.e., an embolization). In order to be effective, an embolic microcoil must apply pressure sufficient to prevent additional blood flow, but not an excessive amount of pressure that causes rupture.
To improve their function, some existing coils include integrated, mesh-like embolic ribbon(s) that extend outwardly in a radial direction from a central support member. Under a cross-sectional view, looking along the longitudinal axis of the central support member, the mesh ribbon and support member are fixedly integrated and/or intersect one another. Such coil structures are typically manufactured using thin metal film. The film is often formed using vapor deposition techniques or by sputtering onto the support member, which is wound onto a core cylindrical mandrel. After the mandrel and support member have been coated with the thin metal film, the mesh pattern is cut using laser, mechanical, or conventional means. While such coils can offer an increased occlusive surface area, they also have a large cross-sectional profile that can create complications during delivery through a microcatheter. This structure may also result in the placement of excessive pressure on the aneurysm wall (thereby risking its rupture), inadequate stability, and/or inadequate biocompatibility with the interior of the aneurysm sac.
Other existing microcoils are overlaid with a fibrous braided cover component. Braided covers are typically formed from stiff metallic wires braided in an overlapping pattern. Like mesh ribbons, braided covers can enhance the ability of the coil to fill and occlude the aneurysm into which it is placed. However, a braided cover exhibits a number of drawbacks as well. The inherent wire-on-wire design creates a stiff configuration that can cause friction during delivery and excessive pressure upon deployment (potentially causing rupture). The wire-on-wire design can also cause undesirable mechanical and/or corrosive wear known as fretting. In addition, the relative motion between wires makes it difficult to incorporate surface treatment and/or therapy options into the cover.
Accordingly, needs exist for an improved microcoil covering that can disrupt blood flow while not risking rupture of the aneurysm. Further, a covering is needed that effectively enables the delivery of surface treatments and other therapies.